A split button couples a primary action with an attached dropdown menu of related actions
Usage & Behaviour
General guidelines
Structure
The split button is separated into two areas: the label/icon and the arrow icon. The separator between them signals that the two areas result in different actions.
The icon which opens the menu acts as a menu (see more information in Drop Down Menu
Content
The label should address the primary action of the button. See additional guidelines in Buttons#Labels
For the items within the menu - by popularity.
Internal Logic
The primary action should appear in the menu, indicated as selected
The Displayed action and menu icon are treated as 2 distinct buttons with their own states See example for hover state:
Default Selection
The primary action should be the most common use case, while the dropdown menu shows a list of related actions
States
State
Image
Comment
Regular
Hover
the color of the button changes and the cursor indicates that you cannot click the split button
Active
Disabled
Error
Interaction
Clicking the primary action on the left, the action is activated.
clicking on the arrow, it exposes a menu of alternative actions
Clicking an action will commit the action and close the menu
If the split button is selected using keyboard actions and then Enter is pressed, the displayed action is activated.
Best practice
Use:
When there are many possible actions but only one primary action
If the actions are related and only one of the actions in commonly used
Don't Use:
For navigation, only for actions
When there are more than 5 action items in the menu
Future Version (TBD)
Semi enabled - When The menu can also contain specific disabled actions while the Primary is enabled and vice versa
Persistent split button - The default is kept until the user makes a different selection which then becomes the default.